The combustion of tobacco produces an aerosol containing gasses and particulate matter, such as tar and nicotine, suspended within the gasses. It is common for cigarette manufacturers to attach filters to tobacco cigarettes or rods to remove tar and nicotine from the aerosol in order to reduce the smoker's exposure to these particles. However, in addition to removing tar and nicotine, filters also remove components of the aerosol which provide tobacco flavor or taste to the smoker.
Various attempts have been made in the prior art to incorporate tobacco extracts and other flavorants in the filter portion of cigarettes to provide enhanced flavor to the smoke while still reducing tar and nicotine. One such example is Woods et al. U.S. Pat. No. 4,729,391. The Woods et al. patent describes a filter construction comprising a conventional cellulose acetate filter tow wrapped with a sheet of microporous polymer, such as polypropylene, having flavorant in amounts of between 0.01% to 6.0% by weight of the filter material adsorbed thereon for release into the smoke stream during smoking of the cigarette.
It is also known in the art to add flavorants to conventional paper and cellulose acetate filters in amounts up to about 10% by weight of the filter material. Such filters are most commonly treated with flavorants in amounts of between 0.1% and 1.0% by weight of the filter material. The addition of flavorants in higher amounts is considered wasteful because most of the flavorant is absorbed into the fibers of the filter material and does not contribute to flavor.
In addition, the conventional tow structure of such filters, in which the filter material is aligned in parallel strips, limits the amount of flavorant that may be added. The orientation of the fibers provides a limited number of interstices in which to trap the flavorant. Thus, even tow filters made of polypropylene, a hydrophobic material which does not absorb flavorants, do not provide much of an advantage over paper or cellulose acetate tow filters due to the limited surface area available to hold flavorants.
Another consideration in producing cigarette filters is the necessity of being able to form the filter material into a rod at commercially acceptable speeds. Conventional rod making machines are not able to form continuous filter material containing tobacco extract in excess of about 10% by weight of the materials into rods, because the tobacco extract builds up on the tongue of conventional rod making machines and thus requires frequent stoppage of the machines to remove the buildup.
Radwanski et al. U.S. patent applicaion, Ser. No. 003,980, filed Jan. 16, 1987, now U.S. Pat. No. 4,961,415 discloses a polypropylene filter web suitable for use as a cigarette filter. Filters produced in accordance with the disclosure of that patent application have a larger number of interstices than conventional tow construction filters. However, industry practice does not suggest that it would be possible or beneficial to add tobacco extracts to such filters in amounts exceeding 10% of the weight of the filter web. Moreover, even if it was beneficial or possible to add tobacco extracts in amounts exceeding 10% by weight, commercial practice suggests that such filters could not be produced at commercially acceptable speeds.
Therefore, a need exists for a cigarette filter and a commerically acceptable method of producing a cigarette filter which offers improved taste characteristics by providing a filter containing tobacco extract in excess of 10% by weight of the filter material.